PM/GC Quilts Skill Builder Series: Part 7 – Quarter Square Triangles

Welcome back for the next entry in the Piecemeal Quilts/Grey Cat Quilts Skill Builder Series! I hope you’ve enjoyed reading the series so far as much as Jeanne and I have enjoyed writing it. This time around I’m talking about Quarter Square Triangles, or QSTs.

Before I get started, I’d like to show you why sometimes it takes me a little longer to accomplish things than I’d like.

Buttercup Helping 5

Buttercup likes to “help” me. I put her on the floor after each of these pictures. In one case she was back on the table before I stood up.

Buttercup Helping 4

Buttercup Helping 3

Buttercup Helping 2

Buttercup Helping 1

Finally, she moved to the quilting frame. I don’t usually like to let the cats do this, but today I was happy that she left me alone.

Buttercup Helping 8

Besides, how ‘dorable is this?

Buttercup Helping 7

Okay, back on track…

Method 1 – Traditional

The traditional method for piecing QSTs involves cutting two (or more) square in quarters diagonally, then sewing the individual pieces back together. The formula for cutting the squares is your finished size (the size the square finishes at once it’s been sewn into a block or quilt) plus 1 1/4″.

Although this method wastes little fabric in theory, it is also require greater accuracy in cutting and sewing. If you decide to use this method, I recommend wasting a little fabric and cutting your squares at finished size plus 1 1/2″, then trimming your finished unit to size.

I started with four different 5″ squares, stacked on top of each other (I actually cut the squares with the fabrics stacked so they are exactly the same, and they’re already lined up perfectly).

Cut the squares diagonally. Notice how the 45 degree line on the ruler lines up with the bottom edge of the squares and the edge of the ruler goes from corner to corner? You don’t have to use the 45 degree line, but it is a nice way to make sure that you cut squares instead of rectangles. If you’ve every accidentally cut a 5″ x 5 1/4″ “square” you’ll understand what I’m talking about.

Do not pull the triangles apart – turn the ruler and cut the other diagonal.

Now you can separate your triangles. The diagonals you cut exposed the bias edges of the fabric (for more on bias, check out Jeanne’s Fabric Fundamentals post). Bias is stretchy, much more so than the straight of grain, so whenever you have an exposed bias edge you need to handle it carefully. Don’t pull on your fabric and don’t push your iron across it.

Lay out your four triangles to form the QST. Value is usually important here, so try to alternate lighter and darker fabrics. You can also use contrasting colors or prints and solids to emphasize the different pieces.

Turn the two right triangles over and place them on the two left triangles. Be aware of which edges you need to sew!

Although it would make sense to put the pointy end of the top triangle through the machine first…

…I like to flip the piece over (still making sure which edge you need to sew) and start on the square edge. Sometimes the machine gets hungry and pulls that point into the feed dogs, causing a thread snarl. Because one of those edges is a bias, you can easily distort the fabric when this happens.

Repeat with the second set of triangles, then press. (In this case I pressed to the darker fabrics, but you should press the top half one direction and the bottom half the other direction, unless you choose to press the seams open, which I’ll get into in the next section.)

Place the two halves right sides together, aligning the long edge and pinching the seams between your fingers to make sure they’re nested tightly together.

(I probably should have pinned here, but the results aren’t too bad.)

The long edge that you’re going to sew is also a bias edge, so try not to stretch it. This time you’ll have to put the pointy end through, so to minimize the chance of the feed dogs eating your point, lift the presser foot and slip the fabric under it…

…then put the presser foot down on top of the fabric. The point is past the leading edge of the feed dogs and the edge of the fabric is just in front of the needle.

Sew, press, and you have a nearly finished QST! I say nearly finished because you still have to trim it, but I explained that in detail in the next section so I won’t repeat it here. By the way, if you look closely, you can see that my seam intersections aren’t quite as nice as I’d like – they’re certainly good enough, but I can do better. That’s caused by a combination of my neglecting to pin the two pieces, and sewing across the seam with the seam allowance pressed toward me (again, I explain this in greater detail below).

Of course I now have a lot of extra triangles with exposed bias edges that I really should use soon. I don’t like having triangles in my scrap bin because the bias edges distort so easily.

This method isn’t really all that difficult, although I struggled with it initially. The most important thing I can emphasize is cut bigger, then trim to size. Yes, it wastes fabric, and yes, it is an extra step, but I’ve found that it reduces frustration and time overall because it is more accurate.

Method 2

There is, however, an easier way. In fact, the only time I would use Method 1 is if I needed to make only one QST unit that had four different fabrics, and I didn’t care if I had a bunch of extra bias-edge-exposed triangles left over. In other words, almost never.

The trick is to start with half square triangles using your favorite method from our first Skill Builder posts. You’ll need to make these a little larger than you would for just HSTs, so add 1/2″ to the finished size of the HSTs. For example, if you want to make 4″ finished QSTs, follow the instructions to make 4 1/2″ finished HSTs.

Using this method, you’ll need at least two HSTS, which will make two QSTs. Fortunately, most blocks that have quarter square triangle units use them in multiples of two, so it works out well.

I’ll demonstrate using the HST method that starts with two squares. In this case, I want to make a 5″ finished QST (that is, it will measure 5″ when it is sewn into a quilt, and 5 1/2″ when it is a separate QST) so I cut two 6 1/2″ squares. (And yes, Buttercup was still helping at this point.)

Draw a diagonal line on the back of one square, then draw another line 1/4″ to each side of that line. Once you’re comfortable with this method, you can eliminate the center diagonal line and just place the 1/4″ line of the ruler on that center diagonal, as I did in these photos.

(Here’s where a ceramic pencil comes in handy – the white line is thin, easy to see and doesn’t require a lot of pressure.)

Place the two squares right sides together and sew just a hair to the center of each line.

Cut on the center line (or where the center line would be if you didn’t draw one). By the way – you just exposed a bias edge, but it doesn’t really matter because you’ve already sewn the pieces together, and the seam keeps the bias from stretching. Another reason to like this method!

Draw a diagonal line on the back of HALF of your HST units, crossing the seam. Measure 1/4″ to each side of the drawn line and draw two more lines. As you can see in the photo, the white line didn’t show up very well on the print fabric, so I used a regular pencil for half of the lines.

Place two HSTs right sides together (one with the lines, one without), with the seams running the same direction. If you are using a background fabric or light/dark values, you want the background (or light) to match up with the print (or dark) on the opposite HST. (I took this photo before I drew the lines – whoops!)

If you pressed your seam allowances to the side, make sure they nest together tightly at the center point. Press on the fabric to feel if there are any lumps or gaps.

Pressing to the side creates a little bulk in the center, but I find that my seam intersections are more accurate with that nesting effect on certain components – QSTs especially. If you prefer to press your seam allowances open, make sure your seams match along the entire length but especially at the very center. It wouldn’t hurt to pin on either side of the center point.

Sew just to the center of each outside line. You’ll be able to trim these to size later, but it is a good idea to stay in the habit of creating “scant” quarter inch seams. With seams pressed to the side, try to sew across them so the seam pressed away from you is on top.

There are two benefits to this – first, if the seam pressed away from you is on the bottom it increases the likelihood that it will catch on the plate of your machine before going under the needle, potentially flipping one or both layers back. Second, the presser foot pushes the nested seam tighter together. If you sewed it in the opposite direction, the presser foot would push the top layer away from the seam intersection rather than toward it, potentially creating a little gap at the points.

Cut along the center line and press the two units. See how the center intersections are all nice and tight? That’s thanks to the tightly nested seams.

Here’s an example with seams pressed open. I pinned the intersection, but I found this more difficult and time consuming than nesting the seams. Sometimes open is great, sometimes I definitely prefer pressing to the side.

I made every effort to sew this accurately, so the slight gaps are not deliberate. You CAN make a neat, accurate QST with seams pressed open, just expect to take a little extra time lining things up.

Here’s an example where the seams weren’t nested tightly because I put them through the machine backward.

Of course, they look worse than they really are because the finished square are very small!

After you’ve sewn the units, you need to trim them to size. It’s an extra step created by cutting the squares slightly larger than necessary, but you’d have to trim the dog ears anyway, so it doesn’t take that much longer. In this photo you can see that the QST unit is 5 3/4″, when we need it to be 5 1/2″.

When you trim your QST units, you MUST measure them from the center point out, NOT from one edge to the other edge.
This requires a little math, but it’s pretty simply. Just divide the unfinished size of the QST (in this case, 5 1/2″) by 2. For this unit that equals 2 3/4″. Find that measurement on your ruler in both directions and put that over the center point of your block. Make sure the 45 degree line on your ruler lines up with the diagonal seam on your QST.

Trim the excess fabric on the first two sides, then turn the QST around, measure 5 1/2″ from the trimmed corner, again making sure your 45 degree line on your ruler lines up with the seam and the 2 3/4″ point is on the center intersecting point, then trim the last two sides. Your QST is finished!

Using QSTs in Blocks

QSTs look fantastic all by themselves, laid out with a 1/4 rotation on alternating blocks.

With a light/dark contrast or background/print fabrics, this is often referred to as an hourglass block. Here I used it to create a couple of baby quilts. (I sent the first quilt off without getting a photo of it quilted. Whoops!)


Hourglass for Allison

You can see a secondary pinwheel on point pattern where the blocks come together.

Another very common traditional block that uses QST units is the Ohio Star. Here’s one example, using Method 2. It went together like a dream!

Everything Old is New Again

And another that splits the blocks diagonally into light and dark halves. This was made using Method 1 back before I knew better.

Ohio Shadows

So, are you ready to tackle a quarter square triangle now? Or have you been making them for ages? Let me know if you have any tips or tricks to add!



  1. Using the companion angle ruler gets you essentially to method #1, but you can often get more efficient use of fabric that way if your fabric is in strips – that’s my method of choice.
    (I also find it awkward to cut a square precisely along its diagonal, moreso for the second cut.)

  2. I have just done Brocante Schnibbles pattern using QST for the first time, some are perfect some are not so perfect… I didn’t know it made a difference which way round I put them in my machine and that the seams can get pushed apart. Thank you for sharing all this Sandi, it really helps me as I have no other way of learning.

  3. Thanks as always for such great tutorials. As a beginner I know I’m very grateful! My orange cat also tries to help out. Usually by pushing my elbow while I’m sewing – doesn’t help with making consistent 1/4″ seams.

  4. The method I use is similar to your second method, but I use Eleanor Burn’s Quilt in a Day triangle square up ruler. It makes the trimming at the end easier for me than just using a regular ruler.

  5. Thanks SEW much for this awesome tutorial!! The best lesson ever!! I learned a lot and have put it into my bookmarks so that I can refer to it when I make HST and QST! Thanks for taking the time to make these tutorials!!

  6. Before I sew the two HS blocks together, I fold (without creasing!) one back to check visually that I’m about to sew it the right way.

    Great tutorial. I think now I understand why my first QST turned out so bad. Inaccurate cutting coupled with feeding it into my sewing machine the wrong way. Once I learned the method you shared, it was much easier to match the points.

  7. i use little snippets of tear away foundation paper or a leader/ender to keep the corner from getting sucked into the machine. but, sometimes i forget…

    buttercup sure is a cutie in your photos. one wouldn’t suspect her of menacing hisses when someone *other than you* sorts scraps on the floor. 🙂

  8. Another great post in the series. I finally got around to starting the We Can Do It! Skill Builder Sampler. I will be referring quite often to your posts (hope you are still ok with that). I realized when reading your Sew Mama Sew article that I didn’t have any square-in-a-square blocks planned! I will have to rectify that.

    Good job on turning something that could have been ugly into such a great resource for us all. 🙂

  9. I think we should start a therapy site for all of us who have the same problem(s). I have to go over everything that comes out of my house with a magnifying glass so I can try not to share the hairs with everyone else. Loved your tutorial, will come back to it later for a more in-depth study.

  10. I just found your site through SMS. This just got me so excited to start on my next quilt! I love that square ruler that you use; I’m going to pick on up before I start on my next project.

  11. My orange kitty helper says hi to yours! I love it when he goes after the sissors when Im cutting, nearly lost a paw that way! Too cute and I cant keep them off the worktable either.

  12. I’m a new follower through RSS feed, glad I found you! I’m expecting a baby in two months so I will give this quilt a happy memory!!!

  13. Ooh, what a pretty kitty! Thanks for all these skillbuilders. I’m having a great time learning from them!

  14. My cousin is having twins and I will be trying to make two baby quilts. I would love to use this one to start things off!

  15. First of all I am sorry with the sad memories that are tied to the quilt as for a happy story my sister had a 3 1/2 months early baby and she is going to be celebrating her fourth birthday this summer and she has no mental problem and is a perfectly happy little girl who had a rough start in this world. As for the quilt I would love to finish it and give it to my sister that is just a year older than me and has been my best friend growing up, she is due september 2. Love your give-a-way! Thanks for being so generous!

  16. My baby is all grown. I do have him on a tape laughing – it’s hilarious. We were just making noises and it tickled him!

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